Whether producing petroleum products, food oils, or natural gases such as ethane, butane and pentane, petro plants use bio-chemical engineering processes to convert raw resources into usable products. Other types of refineries use anhydrous pyrolysis to recycle plastic, rubber or biological waste into crude fuel oil, carbon black and non-condensable gases. Whatever the end final product, the colonists needed it for their burgeoning industrialization. Despite technical advances over the decades on Old Earth, however, there were still significant safety and environmental concerns attendant to plant operations. Hence, some colonies invested heavily in the building of refineries, while others avoided construction so much as possible. The issue would develop into one of the first significant ethical divides separating the various philosophic tenets to settling this planet, most notably between those adopting Harmony and those following a Purity approach. But none could argue with the need for the materials produced, so petro plants remained common in the colonial landscape, with air and wastewater pollution limited – but not eliminated – in a variety of ways.